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Centrifugal pump discharge vs. speed at constant head and geometry Assume impeller diameter and system head remain the same. Describe how discharge varies with rotational speed. Choose the correct relation.

Difficulty: Easy

Discharge is directly proportional to speed (Q ∝ N)
Discharge varies as the square of speed (Q ∝ N²)
Discharge is independent of speed
Discharge decreases as speed increases

Correct Answer: Discharge is directly proportional to speed (Q ∝ N)

Explanation:

Affinity law (similarity)

For geometrically similar operation of a given impeller, Q ∝ N, H ∝ N², and P ∝ N³ (with diameter fixed).

Therefore
At constant head/geometry, increasing speed raises discharge in direct proportion.

Final Answer
Q ∝ N (directly proportional).

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